Production of ultra high melt flow polypropylene resins

ABSTRACT

A method of preparing ultra high melt flow polypropylene having reduced xylene solubles is provided. The method utilizes a diether internal donor-containing Ziegler-Natta catalyst system to polymerize propylene. The polypropylene produced is characterized by having a melt flow of at least about 300 g/10 min and a xylene solubles of not more than about 3.5% and no peroxide residue. The catalyst system may also include an internal phthalate donor. The method of the invention allows the amount of external donors to be reduced, or even eliminated, without significant increases in xylene solubles.

CROSS REFERENCED TO RELATED APPLICATION

[0001] This application is a divisional of co-pending application Ser.No. 10/044,886 filed Jan. 11, 2002, by Kenneth Paul Blackmon, Luis PauloBarthel-Rosa and Shabbir Admedbhai Malbari, under the same title.

[0002] This application claims the benefit of U.S. ProvisionalApplication No. 60/261,705, filed Jan. 12, 2001.

TECHNICAL FIELD

[0003] The invention relates generally to the production ofpolypropylene and, particularly, to the production of ultra high meltflow polypropylene resins, and more particularly, to ultra high meltflow polypropylene resins having low xylene solubles.

BACKGROUND

[0004] Thermoplastic olefin polymers, such as linear polyethylene,polypropylene, and olefin copolymers, are formed in polymerizationreactions in which a monomer is introduced into a reactor with anappropriate catalyst to produce the olefin homopolymer or copolymer. Thepolymer is withdrawn from the catalyst reactor and may be subjected toappropriate processing steps and then extruded as a thermoplastic massthrough an extruder and die mechanism to produce the polymer as a rawmaterial in particulate form, usually as pellets or granules. Thepolymer particles are ultimately heated and processed in the formationof the desired end products.

[0005] Melt flow is the measure of a polymer's ability to flow undercertain conditions. It is typically measured as a melt flow index, whichis the amount of polymer that flows over a period of time underspecified conditions. Typical melt flow units of measurement are g/10min. Melt flow provides an indication of the polymer resin'sprocessability, such as in extrusion or molding, where it is necessaryto soften or melt the polymer resin. Polymer resins produced with a lowmelt flow may need to be further modified after their initialpolymerization to improve their processability. This is typically donethrough controlled rheology (CR) techniques wherein the molecular weightof the polymer is lowered, usually by the addition of peroxide, tothereby improve its flowability. This secondary processing, however,adds additional processing steps and increases the cost ofmanufacturing. Controlled rheology processing may also degrade thepolymer and leave peroxide residue so that its use may be limited incertain applications. As defined herein, “peroxide residue” shall beconstrued to mean the decomposition and reaction products of peroxide,such as tert-butyl alcohol, as well as unreacted peroxide, typicallyfound in CR-modified polymers.

[0006] Polypropylene is most often produced as a stereospecific polymer.Stereospecific polymers are polymers that have a defined arrangement ofmolecules in space. Both isotactic and syndiotactic propylene polymers,for example, are stereospecific. Isotactic polypropylene ischaracterized by having all the pendant methyl groups oriented eitherabove or below the polymer chain. Isotactic polypropylene can beillustrated by the following chemical formula:

[0007] This structure provides a highly crystalline polymer molecule.Using the Fisher projection formula, the stereochemical sequence ofisotactic polypropylene, as shown by Formula (2), is described asfollows:

[0008] Another way of describing the structure is through the use ofNMR. Bovey's NMR nomenclature for an isotactic pentad is . . . mmmm . .. with each “m” representing a “meso” dyad, or successive methyl groupson the same side of the plane of the polymer chain. As is known in theart, any deviation or inversion in the structure of the chain lowers thedegree of isotacticity and crystallinity of the polymer.

[0009] Conventional Ziegler-Natta catalysts are stereospecific complexesformed from a transition metal halide and a metal alkyl or hydride andare used in the production of isotactic polyolefins. Ziegler-Nattacatalyst for the polymerization of olefins are well known in the art.The Ziegler-Natta catalysts are derived from a halide of a transitionmetal, such as titanium, chromium or vanadium with a metal hydrideand/or metal alkyl, typically an organoaluminum compound as aco-catalyst. The catalyst is usually comprised of a titanium halidesupported on a magnesium compound. Ziegler-Natta catalysts, such astitanium tetrachloride (TiCl₄) supported on an active magnesiumdihalide, such as magnesium dichloride or magnesium dibromide, asdisclosed, for example, in U.S. Pat. Nos. 4,298,718 and 4,544,717, bothto Mayr et al. are supported catalysts. Silica may also be used as asupport. The supported catalyst may be employed in conjunction with aco-catalyst such as an alkylaluminum compound, for example,triethylaluminum (TEAL), trimethyl aluminum (TMA) and triisobutylaluminum (TIBAL).

[0010] Ultra high melt flow (UHMF) polypropylene generally has a meltflow of greater than about 300 g/10 min. The production of UHMF polymerscan be achieved during their initial polymerization, without the needfor secondary processing. This usually involves the addition of hydrogenduring the polymerization reaction. Increasing hydrogen concentrationsin the polymerization reactor, however, can result in the production ofexcessive xylene solubles, which is oftentimes undesirable. Equipment orprocess limitations may also limit the amount of hydrogen that can beused during the polymerization reaction.

[0011] The preparation of ultra high melt flow products duringpolymerization is a challenge involving a delicate balance between thedesired melt flow and xylene solubles. Xylene solubles is a measure ofthe crystallinity or tacticity of the polymer, or a deviation from themmmm pentad levels found in isotactic polymers discussed previously.Because increasing hydrogen level generally results in the production ofhigher xylene solubles, external donors have been used to offset orreduce the amount of xylene solubles levels.

[0012] External donors act as stereoselective control agents to controlthe amount of atactic or non-stereoregular polymer produced during thereaction, thus reducing the amount of xylene solubles. Examples ofexternal donors include the organosilicon compounds such ascyclohexylmethyl dimethoxysilane (CMDS), dicyclopentyl dimethoxysilane(CPDS) and diisopropyl dimethoxysilane (DIDS). External donors, however,tend to reduce catalyst activity and tend to reduce the melt flow of theresulting polymer.

[0013] To obtain polymers with the desired high melt flow and reducedxylene solubles, a precise balance between hydrogen concentration andexternal donors must be struck. Therefore, obtaining ultra high meltflow polymers with low xylene solubles through the use of externaldonors has been quite difficult, and oftentimes results in significantproduction of off-grade or unacceptable materials when preciseparameters are not maintained.

SUMMARY

[0014] A method of preparing ultra high melt flow polypropylene havingreduced xylene solubles is provided. The method requires polymerizingpropylene monomer within a reaction zone in the presence of an etherinternal donor-containing Ziegler-Natta catalyst system to yield apolypropylene product having a melt flow of at least about 300 g/10 minand a xylene solubles of not more than about 3.5%. The catalyst systemmay optionally include an external donor or an internal phthalate donor.The method may be carried out with a hydrogen concentration of fromabout 0.3 to about 1.1 mol %.

[0015] An ultra high melt flow polypropylene having reduced xylenesolubles is produced by polymerizing propylene monomer within a reactionzone in the presence of a di- or polyether internal donor-containingZiegler-Natta catalyst system to yield a polypropylene productcontaining no peroxide residue and having a melt flow of at least about300 g/10 min and a xylene solubles of not more than about 3.5%. Thecatalyst system may also include an internal phthalate donor.

BRIEF DESCRIPTION OF THE DRAWINGS

[0016] For a more complete understanding of the present invention, andthe advantages thereof, reference is now made to the followingdescriptions taken in conjunction with the accompanying figures, inwhich:

[0017]FIG. 1 is a plot of melt flow versus hydrogen concentration forgiven catalysts and different donors and a Al/Si ratio of 50;

[0018]FIG. 2 is a plot of melt flow versus hydrogen concentration forgiven catalysts and different donors and a Al/Si ratio of 10;

[0019]FIG. 3 is a plot of xylene solubles versus donor level at lowhydrogen concentrations for given catalysts and donors;

[0020]FIG. 4 is a plot of xylene solubles versus donor levels at higherhydrogen concentrations for given catalysts and donors;

[0021]FIG. 5 is a plot of fluff particle size distribution of polymersproduced utilizing different catalysts and donors;

[0022]FIG. 6 is a plot of hydrogen concentration, melt flow, donorlevels and xylene solubles for a given diether internal donor-containingcatalyst;

[0023]FIG. 7 is a plot of hydrogen concentration, melt flow, donorlevels and xylene solubles for a conventional Ziegler-Natta catalyst;

[0024]FIG. 8 is a plot of catalyst productivity versus donor level trendfor polymer fluff produced from a given diether internaldonor-containing catalyst; and

[0025]FIG. 9 is a plot of xylene solubles versus donor level for a givendiether internal donor-containing catalyst.

DETAILED DESCRIPTION

[0026] It has been found that the use of a Ziegler-Natta catalyst thatincludes a diether or polyether-based internal electron donor for thepolymerization of propylene can yield an ultra high melt flow polymerwith low xylene solubles. This is advantageous because ultra high meltflow allows easier processability and may reduce or eliminate the needfor further processing, such as through controlled rheology techniques.As used herein, ultra high melt flow generally refers to a melt flowof >300 g/10 min as measured according to ASTM D1238-95. TheZiegler-Natta catalysts are those derived from a halide of a transitionmetal, such as titanium, chromium or vanadium, with titanium being thedesired metal. Examples of transition metal compounds include TiCl₄,TiBr₄, TiO(C₂H₅)₃Cl, Ti(OC₂H₅)₃Cl, Ti(OC₃H₇)₂Cl₂, TiO(C₆H₁₃)₂Cl₂,Ti(OC₂H₅)₂Br₂ and Ti(OC₁₂H₂₅)Cl₃. The transition metal compounds may beused individually or in combination. Typical titanium levels are fromabout 1.5% to about 4% by weight of catalyst.

[0027] The transition metal halide is used in combination with a metalhydride and/or metal alkyl, typically an organoaluminum compound as aco-catalyst. Desirably the co-catalyst is an aluminum alkyl having theformula AlR₃, where R is an alkyl having 1 to 8 carbon atoms, with Rbeing the same or different. Examples of suitable aluminum alkyls aretrimethyl aluminum (TMA), triethyl aluminum (TEAL) and triisobutylaluminum (TIBAL). The desired aluminum alkyl is TEAL.

[0028] As discussed previously, the Ziegler-Natta catalyst includes atleast one diether or polyether-based internal donor, which may be usedalone or in combination. Optionally, the Ziegler-Natta catalyst may alsoinclude an internal phthalate donor. The diethers may be represented bythe general formula:

[0029] where R, R₁ and R₂ are linear or branched alkyl, cycloaliphatic,aryl, alkylaryl or arylalkyl radicals with 1-18 carbon atoms, and R₁ andR₂ may also be hydrogen, and where Z is carbon, silicon or germanium,desirably carbon or silicon. Examples of such suitable diether compoundsinclude 2,2-diisobutyl-1,3-dimethoxypropane; 2-isopropyl2-isopentyl-1,3-dimethoxypropane;2,2-bis(cyclohexylmethyl)-1,3-dimethoxypropane,methyl-phenyl-dimethoxymethyl-silane; diphenyldimethoxymethylsilane;methyl-cyclohexyl-dimethoxy-methylsilane;di-tert-butyl-dimethoxymethyl-silane;cyclohexyl-tert-butyl-dimethoxy-methylsilane; andisopropyl-tert-butyl-dimethoxy-methylsilane. Other examples of suitableethers are those listed in U.S. Pat. Nos. 4,971,937 and 5,106,807, whichare incorporated herein by reference. As mentioned previously, otherinternal donors may be present, such as alkyl phthalate donors (e.g.diethyl phthalate, di-isobutyl phthalate). Examples of such donors arelisted in U.S. Pat. No. 5,945,366, which is incorporated herein byreference.

[0030] These internal electron donors are added during the preparationof the catalysts and may be combined with the support or otherwisecomplexed with the transition metal halide. A suitable Ziegler-Nattacatalyst containing a diether-based internal donor compound is thatavailable as Mitsui RK-100 and Mitsui RH-220, both manufactured byMitsui Chemicals, Inc., Japan. The RK-100 catalyst additionally includesan internal phthalate donor. The Ziegler-Natta catalyst is typically asupported catalyst. Suitable support materials include magnesiumcompounds, such as magnesium halides, dialkoxymagnesiums,alkoxymagnesium halides, magnesium oxyhalides, dialkylmagnesiums,magnesium oxide, magnesium hydroxide, and carboxylates of magnesium.Typical magnesium levels are from about 12% to about 20% by weight ofcatalyst. The RK-100 catalyst contains approximately 2.3% by weighttitanium, with approximately 17.3% by weight magnesium, and an averageparticle size of about 13 microns. The RH-220 catalyst containsapproximately 3.4% by weight titanium, with approximately 14.5% byweight magnesium, and an average particle size of about 16 microns.

[0031] The Ziegler-Natta catalyst may also be used with external donorcompounds. External donors are typically organosilicon compounds.External electron donors may be those described by the formulaSiR_(m)(OR′)_(4-m), where R is an alkyl group, a cycloalkyl group, anaryl group or a vinyl group, R′ is an alkyl group, m is 0-4, R may bethe same or different, and R′ may be the same or different. The externalelectron donor acts as a stereoregulator to control the amount ofatactic form of polymer produced, which results is in a decrease inxylene solubles. External donor compounds are known in the art for useas electron donors. Examples of electron donors that are organic siliconcompounds are disclosed in U.S. Pat. Nos. 4,218,339; 4,395,360;4,328,122; 4,473,660 and 4,927,797, which are incorporated herein byreference. Representative examples of external donors includecyclohexylmethyl dimethoxysilane (CMDS), dicyclopentyl dimethoxysilane(CPDS), diisopropyl dimethoxysilane (DIDS), cyclohexylisopropyldimethoxysilane (CIDS), and di-t-butyl dimethoxysilane (DTDS).

[0032] It is noted, however, that although external donors may be used,their use can be decreased to provide ultra high melt flow polymers withlow xylene solubles. Unless specified otherwise, amounts of externaldonor are presented herein as parts per million (ppm) based on theweight of monomer. It is desirable to reduce the amount of externaldonors from zero to about 10 ppm by weight of monomer. Desirably, theexternal donor is used in the range of from about zero to about 5 ppm,with from about zero to about 3 ppm being desired, from about zero toabout 2 ppm being more desired, from about zero to about 1.5 ppm beingeven more desired, from about zero to about 1 ppm being still moredesired, and from about zero to about 0.5 ppm being still more desired.

[0033] As is well known, polypropylene may be produced by slurrypolymerization in the presence of a solvent, e.g. hexane, such as in aloop or CSTR reactor, or by bulk polymerization in which propyleneserves as both monomer and diluent, which is typically carried out in aloop-type reactor. Also, polypropylene may be produced by gas phasepolymerization of propylene, which is typically carried out in afluidized bed reactor. In a typical bulk process, one or more loopreactors operating generally at 50 to 90° C. with pressures of about 400to 600 psi may be used to effect the polymerization of propylene. Thevarious catalytic components, i.e., Ziegler-Natta catalyst, cocatalyst,external donor (if any), are introduced into the reactor, as well as amolecular weight controlling agent (e.g., hydrogen), and the resultingpolypropylene fluff or powder is continuously removed from the reactor.The fluff may then be subjected to extrusion to produce desired pellets.

[0034] Ziegler-Natta catalysts incorporating a diether internal donorcompound were compared to Ziegler-Natta catalysts without such internaldonors. The results showed that the diether-containing catalystexhibited high activity, high hydrogen response, and yielded polymerswith desirable stereoregularity (even in the absence of external donor).Specifically, Mitsui RK-100 was compared to other non-diether-containingZiegler-Natta catalysts that have been used in the production of ultrahigh melt flow polymer materials, particularly polymers with a fluffmelt flow around 350 g/10 min. Certain non-internal-diether-containingcatalysts may exhibit a relatively high hydrogen response, however,formation of significant quantities of off-grade resin have beenencountered with these catalysts due to the difficulty in obtaining thedesired balance of polymer melt flow and xylene solubles level.

[0035] For bulk polymerization utilizing the diether internaldonor-containing catalyst, the single loop reactor temperatures areusually kept from about 50 to about 100° C., more particularly fromabout 60° C. to about 70° C. It should be noted that increasing thetemperature will typically result in an increased catalytic activity andlower xylene solubles. Hydrogen concentrations may vary, but are usuallykept at from about 0.3 mol % to about 1.1 mol %, more particularly fromabout 0.5 mol % to about 0.8 mol % based on monomer, and depending onthe resin melt flow desired. It is of particular note that the method ofthe invention has particular application where hydrogen concentrationsmay be limited, e.g., due to reactor pressure constraints or hydrogensolubility concerns. This is due to the relatively high hydrogenresponse of the diether-containing catalyst. Thus, very acceptableresults can be achieved with hydrogen concentrations of from about 0.5mol % to about 0.6 mol %, and even as a low as from about 0.4 mol % toabout 0.5 mol %.

[0036] The ultra high melt flow polymers produced in accordance with thepresent invention are those having a melt flow after polymerization ofat least 300 g/10 min or greater, as measured according to ASTMD1238-95. Typical melt flows are from about 300 g/10 min to about 1000g/10 min, with from about 300 g/10 min to about 400 g/10 min beingreadily obtainable. Melt flows above 350 g/10 min, 400 g/10 min and evenabove 1000 g/10 min are attainable, while still retaining low xylenesolubles. The polymers produced are also characterized as having lowxylene solubles of not more than about 3.5%, with from about 1 to about3.5% being readily obtainable, and from 2 to about 3.5% being morereadily obtainable, without any significant reduction in melt flow. Asused herein, the terms “propylene polymer” or “polypropylene,” unlessspecified otherwise, shall mean propylene homopolymers or those polymerscomposed primarily of propylene and limited amounts of other comonomers,such as ethylene, wherein the comonomers make up less than 0.5% byweight of polymer, and more typically less than 0.1% by weight ofpolymer.

[0037] The following examples serve to illustrate the present invention.

EXAMPLES 1-5

[0038] In Examples 1-5, propylene polymerization studies were conductedutilizing Mitsui RK-100, Mitsui RH-220 and a conventional internalphthalate-containing Ziegler-Natta catalyst, designated herein asCatalyst X. This conventional Ziegler-Natta catalyst typically containsapproximately 2.8% titanium by weight and approximately 19.2% magnesiumby weight, with an average particle size in the range of 10 to 14microns. The catalysts were tested in the presence of various externaldonors, which included CMDS, CPDS, and DIDS. Hydrogen levels were variedfrom 0.09 to 0.45 mol % at TEAL/donor molar ratios of 10 and 50. Table 1gives the experimental conditions used for the polymerization reactions.TABLE 1 Experimental Conditions for Catalyst Evaluations Reagents:Conditions: catalyst: 10 mg temp.: 70° C. TEAL:      1.0 mmol time: 1hour Ext. Donor: 0.10 or 0.02 mmol propylene: 1.4 L (0.72 kg) Al/Donor:10 or 50 prepolymerization: in situ hydrogen: 0.09 to 0.45 mol %

Example 1

[0039] Catalyst Activity

[0040] The results showed that at lower hydrogen and higher externaldonor levels, the relative productivity of RK-100 was about 5-30% lowerthan that of the conventional Ziegler-Natta catalyst, while the relativeproductivity of RH-220 was about 1.5 times higher than that of theconventional Ziegler-Natta catalyst. However, at higher hydrogen levels(e.g. >0.45 mol %), the productivity of RK-100 was 1.1 to 1.9 timeshigher than that of Catalyst X. The RH-220 catalyst productivity was upto 2 times higher than that of Catalyst X under these higher hydrogenconditions. Thus, the activity benefits of the diether-containingcatalysts at higher hydrogen levels, and particularly, at lower externaldonor levels, were readily apparent.

Example 2

[0041] Melt Flow Performance

[0042] The hydrogen responses of the RK-100, RH-220 and Catalyst Xsystems at low (Al/Si—50) and high (Al/Si—10) donor levels are comparedin FIGS. 1 and 2, respectively, and tabulated in Tables 2 and 3, below.TABLE 2 Catalyst Sample (Al/Si - 50) Hydrogen, mol % Melt Flow, g/10 minRK-100, [CMDS] 0.09 4.6 0.27 16.4 0.45 51.0 RK-100, [DIDS] 0.09 4.4 0.2722.0 0.45 32.0 RK-100, [CPDS] 0.09 4.0 0.27 14.0 0.45 28.0 RH-220,[CMDS] 0.09 3.9 0.45 56.2 Cat. X, [CMDS] 0.09 2.2 0.18 5.6 0.27 7.2 0.4524.0 Cat. X, [CPDS] 0.09 0.7 0.27 2.8 0.36 3.7 0.45 4.7 Cat. X, [DIDS]0.09 1.1 0.27 2.7 0.45 8.4

[0043] TABLE 3 Catalyst Sample (Al/Si - 10) Hydrogen, mol % Melt Flow,g/10 min RK-100, [CMDS] 0.09 3.7 0.27 19.0 0.45 32.0 RK-100, [DIDS] 0.095.0 0.27 19.6 0.45 50.0 RK-100, [CPDS] 0.09 3.2 0.27 14.0 0.45 28.0RH-220, [CMDS] 0.09 4.1 0.45 13.3 Cat. X, [CMDS] 0.09 1.6 0.27 2.9 0.4510.6 Cat. X, [CPDS] 0.09 0.7 0.18 1.0 0.27 2.2 Cat. X, [DIDS] 0.09 0.70.27 3.2 0.45 5.2

[0044] While laboratory results are extremely consistent in establishingpolymer melt flow trends, experience suggests that MFR in actualproduction will usually be significantly higher under certain conditions(i.e., high hydrogen concentration and low external donor levels) thanwhat is seen in the laboratory. This is confirmed in actual productiontrials, which are discussed below. It is evident from laboratory resultsthat the diether internal donor-containing catalyst yields significantlyhigher melt flows under all conditions (i.e., donor, hydrogen level,donor choice) than does the comparative catalyst. At the highesthydrogen concentration (0.45 mol %), the melt flows of samples producedwith RK-100 and RH-220 ranged from about 15 to 50 g/10 min, while thoseproduced with the standard Catalyst X gave melt flows in the 5-10 g/10min range. Similar results were obtained at Al/Si—50 (FIG. 1). Thediether internal donor-containing catalyst RK-100 and RH-220 gavepolymers with melt flows in the 30-55 g/10 min range at the highesthydrogen concentration, while those produced with Catalyst X were in the5-20 g/10 min range. From these results, it is evident that the dietherinternal donor-containing catalysts possess a relatively high hydrogenresponse. As noted previously, the diether internal donor-containingcatalyst activities are also significantly increased at higher hydrogenconcentrations.

Example 3

[0045] Xylene Solubles

[0046] The xylene solubles levels as a function of donor concentrationat low (0.09 mol %—FIG. 3) and high (0.45 mol %—FIG. 4) hydrogen levelsare shown in FIGS. 3-4 and presented in tabulated form in Tables 4 and5, respectively, below. TABLE 4 Catalyst Sample Donor, mmol XyleneSolubles, wt % RK-100, CMDS 0.02 3.6 0.1 1.6 RK-100, DIDS 0.02 3.2 0.12.7 RK-100, CPDS 0.02 2.4 0.1 1.4 RH-220, CMDS 0.02 2.8 0.1 2.0 RH-220,CPDS 0.02 2.5 0.1 2.4 Cat. X, CMDS 0.02 2.4 0.1 1.4 Cat. X, CPDS 0.021.3 0.1 1.1 Cat. X, DIDS 0.02 1.3 0.1 0.9

[0047] TABLE 5 Catalyst Sample Donor, mmol Xylene Solubles, wt % RK-100,CMDS 0.02 3.7 0.1 1.7 RK-100, DIDS 0.02 2.9 0.1 2.3 RK-100, CPDS 0.022.4 0.1 2.1 RH-220, CMDS 0.02 3.2 0.1 1.6 Cat. X, CMDS 0.02 3.7 0.1 1.8Cat. X, CPDS 0.02 1.3 0.1 1.7 Cat. X, DIDS 0.02 1.6 0.1 1.1

[0048] As seen from FIGS. 3-4, the xylene solubles levels decrease withincreasing donor level. At low donor concentration (Al/Si—50), RK-100and RH-220 catalysts gave polypropylene resins with xylene solubleslevels in the 2.5-3.5% range. The standard Catalyst X also gave xylenesolubles of about 1.5%-3.5%. It should be noted that polymerization runswere also made with RK-100 and RH-220 catalysts in the absence ofexternal donor. Without the external donors, the xylene solubles levelsremained relatively low (˜4%). For comparison, the standard Catalyst X(not shown) yielded >20% xylene solubles in the absence of an externaldonor. From these results, it is evident that a conventionalphthalate-containing Ziegler-Natta catalyst could not be usedcommercially in the presence of very low (or no) external donor toobtain ultra high melt flow resins due to the likelihood ofcatastrophically high xylene solubles formation.

Example 4

[0049] Fluff Particle Size Distribution

[0050] The particle size distributions (PSD) of selected fluff samplesproduced with Mitsui RK-100, Mitsui RH-220 and Catalyst X catalysts wereobtained by sieve analyses. The results for polymers prepared withvarious donors (Al/Si—50) at a hydrogen level of 0.27 mol % are shown inFIG. 5.

[0051] As seen from the results, the fluff particle size distributionsfrom RK-100 and RH-220 were more narrow than that for Catalyst X,although the D50 values were similar. Also, the fluff particle sizedistributions from RK-100 and RH-220 were similar for the variousdonors, as well as for the polymer prepared in the absence of donor. Thebulk densities of the fluff samples produced with RK-100 and RH-220(˜0.44 g/cc) were similar to those prepared from the conventionalZiegler-Natta catalyst, Catalyst X (˜0.48 g/cc). From optical microscopy(20×), it was observed that the polymer fluff morphology from RK-100 andRH-220 are “cluster” or “aggregate” in nature, as opposed to that fromCatalyst X which was irregular and granular in appearance.

Example 5

[0052] Thermal and Molecular Weight Properties

[0053] The thermal properties, as measured by differential scanningcalorimetry (DSC), and molecular weight properties, as measured throughgel permeation chromatography (GPC), of representative polymers preparedfrom RK-100, RH-220 and Catalyst X catalysts in the presence of variousdonors are given in Tables 6-7. The selected samples were prepared atAl/Si—50 and 0.27 mol % hydrogen. TABLE 6 Thermal Properties of PolymersPrepared with Mitsui RK-100 and Catalyst X Catalysts Using VariousDonors [Al/Si - 50, 0.27 mol % Hydrogen] Melt Xylene Tm, Run # CatalystDonor Flow Sol., % ° C. ΔHm, J/g Tr, ° C. ΔHr, J/g 1 RK-100 CMDS 16.43.5 156.2/162.9 93.6 107.9 −96.1 2 RK-100 DIDS 22.0 2.5 157.1/163.5 88.2109.1 −96.8 3 RK-100 CPDS 14.0 2.7 158.1/164.5 107.9 108.2 −98.6 4RK-100 None 20 6.0 156.9/163.5 83.2 107.4 −94.2 5 RH-220 CMDS 4.1 2.0161/164 94.3 109.6 −94.2 6 RH-220 CPDS 3.7 2.4 158/164 95.4 108.0 −94.97 RH-220 None 51.8 3.5 156/163 98.5 106.6 −93.6 8 Cat. X CMDS 10.2 5.7160.4 94.1 108.1 −85.6 9 Cat. X DIDS 2.7 1.5 159.4/165.1 106.1 110.1−100.1 10 Cat. X CPDS 3.7 1.3 161.2/166.1 104.2 109.8 −98.9

[0054] From the DSC results, it was observed that the polymers preparedwith the diether internal donor-containing catalyst in the presence ofvarious donors (or no donor) exhibited similar melting points,recrystallization temperatures (107-109° C.), and heats ofrecrystallization (ΔHr). The heat of fusion values showed somevariation, with CPDS yielding the highest ΔHm (107.9 J/g) and no donorthe lowest (83.2 J/g). TABLE 7 Molecular Weight Results for PolymersPrepared with Mitsui RK-100 and Catalyst X Catalysts Using VariousDonors [Al/Si - 50, 0.27 mol % Hydrogen] Mn/ D Run # Catalyst Donor 1000Mw/1000 Mz/1000 (Mw/Mn) 1 RK-100 CMDS 32.8 236.7 933.9 7.2 2 RK-100 DIDS36.4 228.5 847.0 6.3 3 RK-100 CPDS 40.6 258.4 994.5 6.4 4 RK-100 None38.4 225.5 780.2 5.9 5 RH-220 CMDS 50.5 320.0 846.0 6.3 6 RH-220 CPDS60.7 344.0 951.0 5.7 7 RH-220 None 23.8 139.0 405.0 5.8 8 Cat. X CMDS42.3 271.0 882.9 6.4 9 Cat. X DIDS 44.7 458.6 1648 10.3 10 Cat. X CPDS39.3 380.6 1308 9.7

[0055] The GPC results showed the expected trends in that lowermolecular weights (particularly Mw) gave higher polymer melt flows. Itis noted that relatively narrow molecular weight distributions wereobtained with the diether internal donor-containing catalysts RK-100 andRH-220 compared to the previously prepared polymers utilizing thecomparative Catalyst X.

Example 6

[0056] Plant trials were conducted in a single loop bulk polymerizationreactor with the internal-diether-containing Ziegler-Natta catalystMitsui RK-100 with a CMDS external donor for propylene polymerization.The RK-100 catalyst used for the trial contained 2.3 wt. % titanium and17.3 wt. % magnesium. Typical propylene feed rates were on the order of10,000 lbs./hr. The start-up production conditions were as follows:

[0057] Hydrogen Concentration: 0.980 mol %

[0058] Donor Level—2.4 ppm

[0059] Cocatalyst Level (TEAL) 135 ppm

[0060] Reactor Temperature: 145° F. (62.8° C.)

[0061] Percent solids: 33-38% range.

[0062] During polymerization, the hydrogen levels were adjusted toobtain MF's in the 300-400 range and were finally settled at 0.540 mol%. During the trials, the CMDS donor level was reduced several times todetermine the donor response of the catalyst. The cocatalyst level wasnot changed. Specifically, the donor level was reduced as follows:

[0063] Donor from 2.4 ppm to 2 ppm—little, if any, effect on xylenesolubles.

[0064] Donor from 2 ppm to 1.6 ppm—xylene solubles remained in the2.1-2.6% range.

[0065] Donor from 1.6 ppm to 1.2 ppm—xylene solubles remained in the2.1-2.6% range.

[0066] Donor from 1.2 ppm to 1 ppm—xylene solubles remained in the2.1-2.6% range.

[0067] Donor from 1 ppm to 0.6 ppm—xylene solubles remained in the2.5-2.9% range.

[0068] After the external donor had been lowered to 0.6 ppm, analysis offluff samples for % Mg showed increased productivity of about 30%, thusfurther enhancing the benefits of the catalyst at low donor levels.

[0069] The key trends of hydrogen level (mol %×1000) and donor level andthe corresponding fluff melt flows and xylene solubles are summarized inTable 8, below, and in FIG. 6. TABLE 8 RK-100 Catalyst Hydrogen Level0.540-0.980 mol % Fluff Melt Flow Range 280 to 943 g/10 min Donor Range0.6 to 2.4 ppm Xylene Solubles 2.1 to 3.2 wt. %

[0070] The plot depicts the hydrogen levels necessary to obtain meltflows in the desired range and the flat xylene solubles response todonor changes. As evidenced in the plot, when stable production wasachieved (“lined out”) the hydrogen concentration of 0.540 mol % gavecorresponding average fluff MF of ˜350 g/l 0 min, and the donor level of0.6 ppm gave average xylene solubles of ˜2.8%, clearly showing theability of the diether-containing Mitsui RK-100 catalyst to yield thedesirable balance of very high resin melt flow with relatively lowxylene solubles levels.

[0071] For comparison, a similar plot of hydrogen, fluff MF, donor leveland xylene solubles during typical UHMF production with a conventionalinternal-phthalate-containing Ziegler-Natta catalyst designated “Y”, isshown in FIG. 7 and in Table 9 below. TABLE 9 Catalyst Y Hydrogen Level0.980 mol % Fluff Melt Flow Range 255-380 g/10 min Donor Range 2.2-2.4ppm Xylene Solubles 2.4 to 3.8 wt. %

[0072] From the plot, the conventional Ziegler-Natta catalyst requiredabout twice as much hydrogen (0.980 mol %) to give average fluff meltflow rates ˜315 g/10 min with xylene solubles averaging ˜3.1% (and oftenapproaching an undesirable level of >3.5% xylene solubles) at a constantdonor level of 2.4 ppm.

[0073] Production Summary

[0074] The resulting fluff, pellet and xylene solubles results for eachproduct made are listed in Table 10 below. Products designated with “Y”are used to designate products made with the conventional Ziegler-Nattacatalyst, and are listed for comparison. Average values are listed inTable 10, with ranges in parentheses. TABLE 10 Summary of PolymerProperties Fluff MF (g/10 min) Pellet MF (g/10 min) Xsols (%) 1 376(324-550)  756 (629-881) 2.5 (2.1-3.1) 2 363 (320-414)  393 (342-447)2.5 (2.2-3.4) 3 342 (287-367)  360 (304-395) 2.7 (2.5-2.9) 4 341(142-402)  364 (284-405) 2.8 (2.3-3.2) 5 363 (353-373) 1385 (1329-1551)2.8 (2.6-3.1) 2Y 280 (239-369)  325 (272-440) 2.2 (1.7-2.7) 3Y 287(147-427)  331 (250-428) 3.0 (2.0-4.0) 4Y 324 (243-389)  336 (282-415)3.2 (2.4-4.1) 5Y 314 (275-381) 1426 (1197-1870) 2.6 (1.9-3.1)

[0075] As evidenced from the results above, the diether internaldonor-containing RK-100 catalyst gave desirable fluff melt flow rates(˜350 g/10 min), while xylene solubles were <3%.

[0076] Catalyst Productivity

[0077] During testing, the diether internal donor-containing catalystRK-100 productivity was ˜14% higher compared with typical UHMFproduction produced using conventional Ziegler-Natta catalysts.

[0078] Throughout the trial, fluff samples were collected at eachexternal donor level and analyzed for magnesium content to estimatecatalyst productivity. Average productivities (based on % Mg) werecalculated at each donor level. The trend of relative catalystproductivity vs. donor level is plotted in FIG. 8 and the results arelisted in Table 11. As the donor level was decreased from its highestlevel of 2.4 ppm to its lowest level of 0.6 ppm, catalyst productivitywas found to increase by about 30%, as measured by % Mg. TABLE 11Productivities for RK-100 and “Y” Catalyst Catalyst Donor, ppm RelativeProductivity RK-100 0.6 1.3 0.8 1.2 1.0 1.1 1.2 1.0 1.6 1.1 2.0 0.9 2.41.0 Catalyst Y 2.4 1.0

[0079] Xylene Solubles Control

[0080] In laboratory trials, the diether internal donor-containingcatalyst RK-100 was found to give xylene solubles between 3.5-4.5% inthe absence of any added external donor. In contrast, existing catalystsystems with phthalate internal donors gave xylene solubles >20% in theabsence of any added external donor, resulting in a “sticky” fluff. Overthe entire plant trial lasting two weeks, the xylene solubles for RK-100averaged 2.7% (range˜2.1-3.4, of 90 samples analyzed). In comparison, atypical “Y” catalyst resulted in xylene solubles averaging ˜3.2% (range2.4-4.1%, of 39 samples analyzed). For each donor level, the xylenesolubles were averaged together and then plotted vs. donor level asshown in FIG. 9, with the results being listed in Table 12 below. TABLE12 Average Xylene Solubles Catalyst Donor, ppm (wt %) RK-100 0.6 2.8 0.82.7 1.0 2.6 1.2 2.6 1.6 2.6 2.0 2.6 2.4 2.5 Catalyst Y 2.4 3.2

[0081] As can be seen from the plot in FIG. 9, the xylene solublesresponse of RK-100 was relatively flat with decreasing donor level. Theaverage xylene solubles stayed within 2.5-3.0% as donor level wasdropped from 2.4 ppm to 0.6 ppm. Based on a curve fit analysisrepresented of the plotted data represented by the following formula:

y=13.961x ²−5.546x+3.0923  (4)

[0082] where “y” is the average xylene solubles by weight of polymer,and “x” is the donor level in ppm by weight of monomer. From theequation, the xylene solubles are predicted to be ˜3.1% at zero externaldonor level.

[0083] Fluff Characterization

[0084] During trials, spot fluff samples of each product type weretested for thermal and molecular weight properties. The findings arelisted in Table 13 below, along with a typical “Y” catalyst fluffsample. TABLE 13 Thermal, Molecular Weight Properties of Fluff from RKcatalyst Product 1 2 3 4 5 4Y Fluff MF 393 347 347 329 365 302 (g/10min) Xsols (%) 2.3 2.5 2.9 3.2 2.6 3.4 T_(r) (° C.) 108 108 111 111 109106, 111 ΔH_(r) (J/g) −98.4 −97.8 −99.0 −97.7 −97.3 −101.3 T_(m) (° C.)157, 157, 159, 159, 156, 161 159, 165 163 163 164 164 ΔH_(m) (J/g) 98.7102.9 103.0 100.3 98.4 103.7 Mn/1000 13.4 13.9 13.9 14.2 13.5 12.7Mw/1000 73.9 80.4 80.4 80.0 77.2 89.0 Mz/1000 221.7 258.9 260.8 252.4246.7 326.6 D 5.5 5.8 5.8 5.6 5.7 7.0 (Mw/Mn) D′ 3.0 3.2 3.2 3.2 3.2 3.7(Mz/Mw)

[0085] From the above results, it is evident that fluff from the dietherinternal donor-containing catalyst resulted in lower xylene solubles atsimilar melt flows compared to “Y” catalyst. Also, the thermalproperties of the resulting fluff from the diether internaldonor-containing catalyst fell within expected values for homopolymerpolypropylene and compared favorably with the thermal properties offluff from “Y” catalyst (T_(m)˜165° C., ΔH_(m)˜100 J/g, T_(r)˜110° C.,ΔH_(r)˜−100 J/g). It should be noted that the differential scanningcalorimetry (DSC) traces of reactor fluff (which has not been melted,extruded and pelletized) commonly contained shoulders giving rise to thelisting of two melting peaks, whereas pellet samples generally showedonly one melting peak. From the molecular weight data, it was seen thatdiether internal donor-containing catalyst produced fluff with anarrower molecular weight distribution (D˜5.5-5.8, D′˜3.0-3.2) comparedto “Y” catalyst (D˜7.0, D′˜3.7).

[0086] Spot fluff and pellet samples of Product 1, which is processedusing controlled rheology techniques from a MF of 350 up to ˜750 g/10min, were collected to verify peroxide addition and expected narrowingof the molecular weight distribution. In addition, fluff and pelletsamples of Product 4, which was not subjected to controlled rheology,were collected to ensure that unexpected vis-breaking did not occur inextrusion. The molecular weight properties of the fluff and pelletsamples were determined and the results are listed below in Table 14.TABLE 14* Comparison of Fluff and Pellet Thermal and Molecular WeightProperties Product 1 1 4 4 Sample Fluff Pellet Fluff Pellet MF 296 692392 383 (g/10 min) Xsols (%) ---- ---- 2.7 2.7 T_(r) (° C.) ---- ----111 116 ΔH_(r) (J/g) ---- ---- −99.8 −99.3 T_(m) (° C.) ---- ---- 159,165 160 ΔH_(m) (J/g) ---- ---- 103.7 97.9 Mn/1000 14.3 14.7 13.7 13.7Mw/1000 85.0 78.7 78.2 80.9 Mz/1000 273.5 239.7 252.4 264.9 D 5.9 5.45.7 5.9 (Mw/Mn) D′ 3.2 3.0 3.2 3.3 (Mz/Mw)

[0087] In comparing the fluff and pellet molecular weight data forProduct 1, the molecular weight distribution further narrowed (D˜5.4,D′3.0) upon addition of peroxide. For Product 4, the molecular weightproperties and distributions of the fluff and pellet samples weresimilar in the absence of any added peroxide, thus verifying thatunexpected chain degradation did not occur in the extruder. In addition,the thermal properties of Product 4 fluff and pellets were similar, andthe pellet samples showed only one melting peak (T_(m)=160° C.), asdiscussed above. All of these results confirm that the ultra high meltflow resins produced with the diether-containing Mitsui RK-100 catalystpossess expected and desired thermal and molecular weight properties.

[0088] The ultra high melt flow polypropylene resins of the inventionhave particular application in forming melt blown fibers, where a highmelt flow is necessary. These fibers can be used in forming textilematerials, particularly nonwoven textiles. Such nonwoven textiles formedfrom melt blown fibers are often used in surgical coverings, such asdrapes, gowns and masks. Textiles formed from such fibers can also beused in absorbent articles, such as diapers and feminine hygieneproducts. Additionally, the ultra high melt flow polypropylene resins ofthe invention can be used in glass composites as a binder material andin film coatings, wherein the resin is applied to the surface of filmsor other substrates. The polypropylene may also be used in certaininjection molding applications when compounded with fillers (e.g. talc,calcium carbonate, glass, etc.) or other resins, such as EPR rubber, tomanufacture automotive-related articles (e.g. bumper fascia, external orinterior trim, body panels, and the like), appliance parts (e.g.external and internal appliance components and trim) and thin-walledpackaging, such as containers, cups, etc.). Because the resin materialsof the invention have low xylene solubles they may be particularlysuited for use in medical or food handling applications, such drapes,gowns, masks, gloves, food packaging, plates, cups, bowls, foodcontainers, etc.

[0089] Ultra high melt flow polymer resins can be prepared duringpolymerization without the need for further processing, such as throughcontrolled rheology techniques. This may reduce manufacturing costs andprocess steps that would otherwise be needed. Also taste and odor issueswhich result from peroxide residues from the addition and decompositionof peroxides added during controlled rheology are avoided. The amount ofexternal donor compounds can be reduced, if not eliminated, while stillobtaining polymers with low xylene solubles. This can result in anincreased catalyst activity. Because the diether internaldonor-containing catalyst exhibits a higher sensitivity to hydrogen, thepolymerization can be carried out with reduced hydrogen concentration.This is advantageous where high hydrogen concentrations are notpractical, but where high melt flow is desirable.

[0090] While the invention has been shown in only some of its forms, itshould be apparent to those skilled in the art that it is not solimited, but is susceptible to various changes and modifications withoutdeparting from the scope of the invention. Accordingly, it isappropriate that the appended claims be construed broadly and in amanner consistent with the scope of the invention.

We claim:
 1. A polypropylene comprising a propylene polymer having noperoxide residue and having a melt flow of at least about 300 g/10 minand a xylene solubles of not more than about 3.5%, and wherein thepropylene content of the polymer is from 99.5 to 100% by weight ofpolymer.
 2. The polypropylene of claim 1, wherein the polypropylene hasa xylene solubles of from about 1% to 3.5%.
 3. The polypropylene ofclaim 1, wherein the polypropylene has a melt flow of from about 300g/10 min to 1000 g/10 min.
 4. The polypropylene of claim 1, wherein thepolypropylene has a melt flow of from about 300 g/10 min to 400 g/10min.
 5. The polypropylene of claim 1, wherein the polypropylene has amelt flow of at least about 350 g/10 min.
 6. The polypropylene of claim1, wherein the polypropylene has a melt flow of at least about 400 g/10min.
 7. An article formed from the polypropylene of claim 1, wherein thearticle is selected from a group consisting of a polypropylene fiber, atextile material, a diaper, a feminine hygiene product, an automobilebumper fascia, exterior or interior trim or body panel, an internal orexternal appliance component or trim, a drape, a gown, a mask, a glove,food packaging, a cup, a plate, a bowl, and a food container.
 8. Amaterial formed from the ultra high melt flow polypropylene of claim 1,wherein the material is selected from a group consisting of a coatingmaterial for applying to a substrate and a binder material.